INTRODUCTION

The emergence of the Covid-19 pandemic necessitated the administration of safe and effective vaccines. The vaccine also needed to be given to sufficient numbers of people to achieve the herd immunity required to halt transmission of the virus, as well as the health and mortality impacts and the negative effects on the economy. There was thus a rush to produce vaccines, but these had to be produced at scale, priced affordably and made available globally. Vaccines also had to be authorized or approved for human use. Each country had to choose whether to use only vaccines approved by the World Health Organization (WHO) or to expand their choices based on their assessment of the available vaccines and their country's needs. The supply of vaccines to a country, especially to developing countries with no capacity to produce their own, became a critical factor in managing the pandemic. Procuring vaccines has become a serious challenge for many developing countries (Sheikh et al. 2021), including those in Southeast Asia. Local production can also support supply since some developing countries do have the capacity to manufacture vaccines. Unfortunately, intellectual property rights and limited technology transfer can stand in the way of local production (OECD 2021). Vaccines were not accessible in most developing countries at the end of 2020 when they were first authorized for use, because high-income countries had pre-purchased a significant portion (Tagoe et al. 2021). Given budget constraints, developing countries had to consider different supply sources, including donations and aid.

In 2020, it was already established that several leading vaccines required ultra-cold storage and transport chains and had short shelf lives once removed from the ultra-cold conditions. Hence, the deployment of vaccines also depends on a country's logistics infrastructure, capacity and capability (OECD 2021). There can also be significant variations within a country, namely between better-developed urban areas and logistically challenged rural regions.

Another challenge that remains even once supplies are made available is the state's capacity to distribute and administer the vaccines to their entire populations, taking into account the risk factors of different age groups and vulnerabilities, geographical constraints and sociocultural factors (Tevdovski, Jolakoski, and Stojkoski 2022). A state's capacity to implement a viable and effective vaccination strategy is therefore another key factor that can influence a country's vaccine roll-out.